1. Field of the Invention
The present invention relates to a brush seal device for sealing a clearance between a rotary shaft and a mating component that are relatively movable. More particularly, the present invention relates to a brush seal device that is disposed between two components relatively movable in, for example a gas turbine and an airplane and seals the clearance in away that a brush seal is deformed to follow the change in the movement of one component even if the one component changes slightly its movement relative to the other component.
2. Description of the Related Art
As a related art to the present invention there exists a brush seal device 100, as shown in FIG. 9.
FIG. 9 is a sectional view of a brush seal device 100 mounted between a rotary shaft 120 and a casing 110 through which the rotary shaft 120 passes. The casing 110 is a fixed component of, for example, a steam turbine or a gas turbine. The brush seal device 100 attached to the casing 110 seals fluid to be sealed between the casing 110 and the rotary shaft 120.
In FIG. 9, the brush seal device 100 is formed in the shape of a ring and its attachment section 104 on its outer circumference is attached to a channel portion 112 of the casing 110. Main components of the brush seal device 100 are a brush seal 109, a backing plate 102, and a support plate 103. In the brush seal 109, bristles 101 are arranged around a circular circumference to form a wall having a certain width and with their outer ends being coupled to form an attachment section 104. The free end 105 on the inner circumference side of the brush seal 109 faces the rotary shaft 120. The diameter of a bristle 101 generally used is 0.20 mm or more.
An annular backing plate 102 is disposed on a side face of the brush seal 109 with its side face 108 being in contact with the brush seal 109, supporting the bristles 101 against the action due to the pressure of the sealed fluid.
A support plate 103 formed as a ring plate is disposed on the other side face of the brush seal 109 to sandwich, in cooperation with the backing plate 102, the brush seal 109 on its attachment section 104 side, thereby to couples them in a body. The inside diameter of the support plate 103 is made large so that the sealed fluid can effect on the side face of the brush seal 109. The brush seal 109 is exposed at its free end 105.
Outer circumference sides of the backing plate 102, the attachment section 104 of the brush seal 109, and the support plate 103 are welded to form a connecting section 106.
FIG. 10 is a front view of the brush seal 109. The brush seal 109 in FIG. 10 is in a state that the brush seal 109 and the rotary shaft 120 are normally fitted without oscillation, such that the bristles 101 extend straight and oriented to incline relative to the radial direction of the rotary shaft 120. In the normal state of the brush seal 109, the rotary shaft 120 is in contact with or close to the free end 105, as shown by the solid line in FIG. 9.
Another related art is also shown in FIG. 11. In the drawing, a connecting section 106 of a brush seal 109 is contained within an attachment section 131 of a brush holder 130 and is allowed to move in the radial direction. A plate spring 132 urges the connecting section 106 to bear in the radial direction of the rotary shaft 120.
When the rotary shaft 120 eccentrically presses against the brush seal, it becomes complex to calculate two spring constant, one corresponding to the resilient deformation of bristles, and the other to the resilient deformation of the plate spring 132, due to the involvement of the complexity in friction generated from its mounting structure. Since those two spring constants and other frictions are the elements for the design of the device, it is extremely difficult to achieve optimum design or improvement in consideration of the pressure generated by the displacement of the rotary shaft 120. Thus, the ability of the bristles 101 to follow the displacement of the rotary shaft 120 is not fully performed and it results in quick abrasion of the free end 105 of bristles.
In addition, the ability of the bristles 101 having a larger diameter to follow is poor when the bristles contact the rotary shaft 120. Moreover, as the thickness of a bundle of bristles becomes larger, the ability to follow becomes poorer. Accordingly, it is limited to make the thickness of the bundle of bristles large. Thus, the sealing ability is necessarily reduced.
In the brush seal device 100 configured as above, while the brush seal 109 is pressed against the rotary shaft 120 as shown in FIG. 12, when eccentricity or vibration causes the rotary shaft 120 to contact the brush seal 109, its tilt angle is further increased.
In this condition, if the pressure of the sealed fluid is high pressure (P1), since the differential pressure (P1-P2) between the high pressure (P1) and the low pressure (P2) becomes large as shown in FIG. 9, the entire straight bristles of the brush seal 109 are pressed against the backing plate 102 and then it becomes difficult for them to deflect in response to the contact with the rotary shaft 120, that is, the ability to follow in response to the rotary shaft 120 is worsened. Also, when the sealed fluid flows into spaces between bristles 101, each bristle 101 is easily pushed apart and thus the tilted bristles 101 tend to displace at its side pushed apart such that tilt angle becomes smaller, thereby to form clearances among the bristles 101. Then the bristles 101, each of which was pushed apart and has a small tilt angle transit to the state that their length in the radial direction are longer. Accordingly, pressure exerted by the rotary shaft 120 is further increased to wear the bristles.
In routing such behaviors as describe, the clearance C that is given between the free end 105 of the bristles 101 on the side diametrically opposite to the side where the brush seal 101 is pressed against the rotary shaft 120, as shown in FIG. 12, is extended as shown in FIG. 13, causing leakage of the sealed fluid out of the clearance C.
The present invention has been made in consideration of the problems as mentioned above and the technical problems to be solved are: to reduce the resilient force exerted on the brush seal caused by the pressure of the rotary shaft so that abrasion of the brush seal by the rotary shaft can be reduced; to improve the ability of the brush seal to follow in response to the change of the rotary shaft for increasing the sealing ability; and to achieve to obtain a brush seal in the shape of a rectangular strip so as to allow resilient deformation and increase the sealing ability.
The present invention has been made to solve the problems as described above, and technical means for solving them are constituted as below.
A brush seal device of a preferred embodiment according to the present invention is one which is mounted to one of two components rotatable each other with a clearance there between, and seals the clearance, comprising: a brush seal having an attachment section for fixing one end of a row of bristles arranged in the shape of a wall and having a free end facing the surface of the other component, wherein each of the bristles in the brush seal has a bending portion in the middle for facilitating resilient buckling deformation of the bristle.
In the brush seal device of a preferred embodiment according to the present invention, in the middle of a bristle of a brush seal is defined a bending portion for facilitating resilient deformation, and the flexible bending portion can be deformed resiliently when action force from a rotary shaft exerts on the free ends of the bristles, to follow the circumference of the rotary shaft, and the sealing ability will fully perform. The brash seal may be in the shape of shape of rectangular strips, as well as the shape of wire, thereby to improve the sealing ability. Furthermore, it is allowed to reduce abrasion due to the contact of the free end of the brush seal with the circumference of the rotary shaft.
Additionally, with the ability of the bristle to follow the movement of the rotary shaft, it is easy to calculate spring constants based on the bristle and the force acting on the bristle without further calculation for other elements, resulting in easy optimum design.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-198813, filed on Jun. 29, 2001, the disclosure of which is expressly incorporated herein by reference in entirety.